Refractory composition and method of preparation



United States Patent This invention relates to an improved periclase refractory composition and to the method of preparing it.

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or SiO they are present in minor amounts as impurities. We briquette the mixture and fire it at a temperature of about 2800 to 3100 F. Next we crush the fired product and grind it into suitable grain size fractions for brickmaking. We may use this prepared grain as all or only a portion of a total brick batch. We have found we gain the greatest advantage when we use the grain as approximately one-fifth to one-half the batch, either as a coarse grain fraction or as ball-mill fines, the balance being 95 to 98 percent MgO periclase.

The following table furnishes specific examples which demonstrate the advantages of our invention:

Comparison of properties for commercial and experimental periclase brick Description of Brick Modulus of Rupture,

Burning Apparent p.s.i. at- Relative Temp., F. Porosity, Slag percent E rosion 1 Coarse Fraction 60% Fine Fraction 2,300 F. 2,700 F.

Ctmnelricial Grain with Normal CaO/ 16-21 280-375 80-150 0.9-1 .3

1 z atlO. CoRmmercial Grain with High CaO/SiOi 16-20 600-1, 550 280450 0.8-1 2 atio. Synthetic Grain Made From Magnesia 3, 100 20.3 450 2 ND 0.8

+21% SrO and 2.1% A1203. Commercial 97% MgO Grain Synthetic Grain Made From 2,800 16 .3 1, 550 880 0.6 Magnesia+2.1% SrO and 3, 100 15.2 1, 580 1, 080 0.5 2.1% A1203. Synthetic Grain Made From Magnesia Commercial 97% MgO Grain-. 2, 800 16 .8 1, 450 1, 020 0.5 +21% SrO and 2.1% A1203. 3, 100 15 .8 1, 600 1, 250 0.5 Commercial 97% MgO Grain V Commercial 97% MgO 2,800 17.5 1, 600 1, 250 ND Grain Synthetic Grain 3, 100 16.3 1, 600 1,390 ND Made From Magnesia+2% SrO and 4% A1203.

1 Relative Indices; Burned Periclase Brick=l.0 (low number less erosion).

; Not Determined.

An object of the invention is to provide an improved periclase refractory composition which is especially suited for making brick used in basic oxygen steelmaking furnaces and having superior hot strength and resistance to slagging.

A further object is to provide a composition of the foregoing type and a method of preparing it in which we incorporate alumina and strontium oxide in the periclase in critical proportions.

According to our invention, we lightly calcine magnesia at a temperature of about 1800 to 2500 F. The magnesia should have an MgO content of at least 95 to 98 percent or preferably 97 to 98 percent. We mix with the calcined magnesia about 1 to 5 percent by weight SrO and about 1 to 8 percent by weight A1 0 or preferably 1 to 2 percent SrO and 2 to 4 percent A1 0 We may add the SrO as the carbonate, sulfate or oxide, and the A1 0 as oxide or other forms which yield oxide on calcining. The ratio of SrO to A1 0 should be 1 or less, and the ratio of SrO plus CaO to Si0 should be at least 2 to 1. Although we normally do not add either G10 From the foregoing description and examples, it is seen that our invention affords a refractory composition of particularly desirable characteristics for brick used in basic oxygen steelmaking furnaces, both as to mechanical strength at high temperatures, and resistance to slagging. We attain these results with controlled additions of A1 0 and SrO. We believe the results are unexpected, since the prior art leads one to believe the A1 0 content of bricks of this type should be kept to a minimum.

While We have described only certain preferred modes of practicing our invention and preferred ranges, it is apparent other modifications may arise. Therefore, we do not wish to be limited to the disclosure set forth, but only by the scope of the appended claims.

We claim:

1. A refractory composition for use in making brick consisting of lightly calcined magnesia, about 1 to 5 percent by weight SrO, and about 1 to 8 percent by weight A1 0 the maximum ratio of SrO to A1 0 being 1.

2. A composition as defined in claim 1 in which the magnesia is about to 98 percent MgO, the content of 3 SrO is about 1 to 2 percent, the content of A1 0 is about 2 to 4 percent, and the ratio of SrO plus CaO to Si0 is at least 2 to 1.

3. A method of preparing a refractory composition for use in making brick comprising mixing with lightly calcined magnesia about 1 to 5 percent by weight SrO and about 1 to 8 percent by weight A1 0 to provide a maximum ratio of SrO to A1 0 of 1, briquetting the mixture, firing the briquettes at a temperature of about 2800 to 3100 F., and crushing the fired briquettes.

4. A method of preparing a refractory composition for use in making brick comprising mixing with lightly calcined magnesia about 1 to 5 percent by weight S10 and about 1 to 8 percent by weight A1 0 to provide a maximum ratio of SrO to A1 0 of 1, the magnesia having.

an MgO content of about 95 to 98 percent, the ratio of SrO plus CaO to SiO in the mixture being at least 2 to 1, briquetting the mixture, firing the briquettes at a temperature of about 2800 to 3100 F., and crushing the fired product. a

5. A method as defined in claim 4 in which the proportion of SrO is about 1 to 2 percent, the proportion of A1 0 is about 2 to 4 percent, and the MgO content of the magnesia is about 97 to 9 8 percent.

References Cited by the Examiner UNITED STATES PATENTS 2,063,543 12/1936 Erdmann 10662 2,336,360 12/1943 Kleinschmidt et a1. 10662 2,695,242 11/1954 Woodward 106-62 TOBIAS E; LEVOW, Primary Examiner.

J. E. POER, Assistant Examiner. 

1. A REFRACTORY COMPOSITION FOR USE IN MAKING BRICK CONSISTING OF LIGHTLY CALCINED MAGNESIA, ABOUT 1 TO 5 PERCENT BY WEIGHT SRO, AND ABOUT 1 TO 8 PERCENT BY WEIGHT AL2O3, THE MAXIMUM RATIO OF SRO TO AL2O3 BEING
 1. 